Cellulose organic acid ester plastic containing resorcinol monobenzoate



Patented Feb. 17,

CELLULOSE ORGANIC ACID ns'rsn PLASTIC CONTAINING ncsoncmon MONOBENZO- ATE Lester w. A/Meyer and William M. Gearhart, Kingsport, Tenn., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application May 4, 1945,

Serial No. 592.072

3 Claims. (Cl. 106-180) This invention relates to cellulose organic acid ester plastics, and more particularly to the stabilization of such plastics.

As is well known in the art, plastics having excellent properties for a great many purposes can be prepared from cellulose organic acid esters, such, for example, as cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate-propionate and cellulose acetate-butyrate, with suitable plasticisers. Many examples of suitable plasticizers are shown in the art. The fcshoice of plasticizers forms no part of our invenion.

However, cellulose organic acid ester plastics have not been entirely suitable for use in places where they are exposed to a considerable amount oi ultra-violet light: 9. g., out or doors. After one or two months of outdoor exposure in a-sunny climate, the plastic bleached and became increasingly brittle until, at the end of from three to six months, depending on the severity of the climate, crazing occurred. The rapid deterioration of appearance was accompanied by an equally rapid breakdown of physical properties such as strength.

Some compounds whose addition to the plastic composition inhibited physical breakdown of the plastic, caused intense discoloration when the plastic was exposed for any length of time to sunlight or other source of ultra-violet light.

We have found that the addition of a small proportion of resorcinol monobenzoate,

tics containing resorcinol monobenzoate, we have employed outdoor exposure in Arizona, Florida, and Tennessee, as well as an accelerated weathering test in the Kline sunlightrfog chamber, ASTM 2 in section 3-14 of the Federal Specification for Plastics, Organic; General Specifications (Methods of Tests) L-P-406a, Method No. 6021, pages 57, 58 and 100, published by the U. 8. Treasury Department, Federal Specifications Division. Two hundred hours under this test has been found to be roughly equivalent to one year of weathering in Washington, D. C. However, the

climates of Florida and Arizona are much more severe as to ultra-violet light than the climate of Washington, D. C. In the Kline accelerated test, when samples 0.050"-0.075" thick are used, the bleaching-brittleness stage of a plasticized cellulose organic acid ester plastic containing no ultra-violet inhibitor is reached in about 180-200 hours. Crazing occurs in 200-250 hours exposure,

Designation D620-41T. This test is described although occasionally 300 hours is reached without crazing. but with the development of brittleness. Similar samples of plasticized cellulose organic acid ester plastics of the same compositions, but containing in addition 1% (based on the weight of cellulose ester) of resorcinol monobenzoate, withstood more than 1600 hours in the Kline accelerated test before falling, Correspondingly favorable results are indicated by the progress of outdoor exposure tests.

Resorcinol monobenzoate is advantageously introduced into a cellulose organic acid ester plastic at the time the cellulose ester is compounded with the plasticizer. This compounding may be accomplished by any of the known methods, in-

cluding the method of working on hot rolls described in Conklin's U. S. Patent No. 2,155,303.

Resorcinol monobenzoate causes no substantialdiscolcration of the plastic, even when the hotrolling method of compounding is employed, and no substantial discoloration takes place during either outdoor exposure or accelerated testing, By way of illustration, we give the following examples of making up cellulose organic acid ester plastics containing resorcinol monobenzoate. It will be understood that these illustrations do not constitute a limitation oi our invention, which is defined in the appended claims.

Example 1 480 grams of cellulose acetate-butyrate contalning approximately 12'/,% acetyl and 37% butyryl, 40 grams of triphenyl phosphate, and 9.6 grams of resorcinol m'onobenzoate are dissolved in a mixture of 1640 cc. of ethylene dichloride and 288 cc. of methanol. A sheet is formed from the resulting dope by spreading it on a smooth surface and allowing the solvent to evaporate.

Example 2 100 parts by weight of cellulose acetate-butyrate containing approximately 12%% acetyl and 37% butyryl, 14 parts by weight 01' dibutyl sebacate, and 1 part by weight of resorcinol monobenzoate are worked together on hot rolls by the method described in the Conklin Patent No. 2,155,303. Sheets are rolled from the plastic mass thus obtained.

Example 3 Cellulose acetate is substituted for the cellulose acetate-butyrate 0! Example 2.

Any of the known plasticizers for cellulose organic acid esters, such, for example, as dibutyl phthalate, dibutyl sebacate, methoxy-ethyl stearate, trlcresyl phosphate, butoxy-ethyl phthalate, diamyl phthalate, ethyl p-toluene suli'onamide, etc., may be used. In the case of the softer cellulose esters, such as cellulose acetate-butyrate, plastics may even be formed without the use of any plasticizer.

What we claim as our invention and desire to be secured by Letters Patent oi. the United States is:

1. A cellulose organic acid ester plastic comprising a cellulose organic acid ester selected from the group consisting of cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate-propionate and cellulose acetate-butyrate. a plasticizer therefor, and, as an agent for inhibiting deterioration of the plastic by ultra-violet light, approximately 1%-2% based on the weight of the cellulose ester, of resorcinol monobenzoate.

2. A cellulose acetate-butyrate plastic comprislng cellulose acetate-butyrate, a plastlclzer therefor. and, as an agent for inhibiting deterioration of the plastic by ultra-violet light, approximately 1%-2%, based on the welght'oi the cel- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,973,488 Kocher Sept. 11, 1934 FOREIGN PATENTS Number Country Date 492,558 Great Britain Sept. 22, 1918 

